2
Integrated Silicon Solution, Inc. — www.issi.com —
1-800-379-4774
Rev. 00D
06/02/08
IS42S32200E
GENERAL DESCRIPTION
The 64Mb SDRAM is a high speed CMOS, dynamic
random-access memory designed to operate in 3.3V
memory systems containing 67,108,864 bits. Internally
configured as a quad-bank DRAM with a synchronous
interface. Each 16,777,216-bit bank is organized as 2,048
rows by 256 columns by 32 bits.
The 64Mb SDRAM includes an AUTO REFRESH MODE,
and a power-saving, power-down mode. All signals are
registered on the positive edge of the clock signal, CLK.
All inputs and outputs are LVTTL compatible.
The 64Mb SDRAM has the ability to synchronously burst
data at a high data rate with automatic column-address
generation, the ability to interleave between internal banks
to hide precharge time and the capability to randomly
change column addresses on each clock cycle during
burst access.
A self-timed row precharge initiated at the end of the burst
sequence is available with the AUTO PRECHARGE
function enabled.
Precharge
one bank while accessing one
of the other three banks will hide the
precharge
cycles and
provide seamless, high-speed, random-access operation.
SDRAM
read and write accesses are burst oriented starting
at a selected location and continuing for a programmed
number of locations in a programmed sequence. The
registration of an ACTIVE command begins accesses,
followed by a READ or WRITE command. The ACTIVE
command in conjunction with address bits registered are
used to select the bank and row to be accessed (BA0, BA1
select the bank; A0-A10 select the row). The READ or
WRITE commands in conjunction with address bits reg-
istered are used to select the starting column location for
the burst access.
Programmable READ or WRITE burst lengths consist of
1, 2, 4 and 8 locations or full page, with a burst terminate
option.
FUNCTIONAL BLOCK DIAGRAM
CLK
CKE
CS
RAS
CAS
WE
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
BA0
BA1
A10
COMMAND
DECODER
&
CLOCK
GENERATOR
MODE
REGISTER
REFRESH
CONTROLLER
REFRESH
COUNTER
SELF
REFRESH
CONTROLLER
ROW
ADDRESS
LATCH
MULTIPLEXER
COLUMN
ADDRESS LATCH
BURST COUNTER
COLUMN
ADDRESS BUFFER
COLUMN DECODER
DATA I N
BUFFER
DATA OUT
BUFFER
DQM0-3
DQ 0-31
V
DD
/V
DDQ
GND/GNDQ
11
11
11
11
32
32 32
32
256
(x 32)
2048
2048
2048
ROW DECODER
2048
MEMORY CELL
ARRAY
BANK 0
SENSE AMP I/O GATE
BANK CONTROL LOGIC
ROW
ADDRESS
BUFFER
